The most widely used methods (dental age, body weight) for age estimation in nonhuman primates are inadequate. More precise standards and age indicators are needed and can be obtained by measuring skeletal age, which has proven to be the best criterion for assessment of chronological age. Our longitudinal radiographic studies will provide information on the development and bone maturation of the hand and wrist in Macaca mulatta monkeys. The data will cover the entire period of appendicular bone maturation, from 120 days of gestation (the onset of carpal center ossification) to adulthood (over five years). To obtain the fetal data, a novel surgical technique of multiple uterotomies was developed. Serial radiographic data are obtained at three uterotomies and after delivery. The pre- and postnatal age indicators will be prepared for publication as an atlas, which should make the data readily unsable in many studies where the precise age of the experimental animal is required.